The overall goal of this research is to contribute to the understanding of the biochemical mechanisms of the induction of periodontal disease in man. The biosynthesis of a virulence-associated surface antigen will be studied in Actinomyces viscosus T14, a human oral bacterium that forms plaque and that evokes massive periodontal disease in experimental animals. The virulent organism possesses an antigen that is absent from a mutant, avirulent strain. This "virulence-associated antigen" (VAA) consists of a polysaccharide covalently linked to a fragment of peptidoglycan. The major carbohydrate constituent of the antigen is 6-deoxytalose (DOT). It is expected that the VAA is a constituent of the cell wall and plays an important role in the mechanism by which the organism evokes periodontal disease. The incorporation of radioactive DOT from TDP-6-deoxytalose into chromatographically immobile material will be assayed. The dependence of DOT incorporation upon nucleoside diphosphate sugars (glucosamine, rhamnose, galactose) as well as the TDP-6-deoxytalose dependence of incorporation of carbohydrate from these other nucleotide sugars, will tentatively establish the carbohydrate content and sequence of VAA. The identity of the radioactive, synthetic polymer will be verified by analysis of the hydrolysis products and by precipitation with specific antiserum. If the DOT-containing antigen is indeed essential in the pathogenicity of A.viscosus T14, the absence of DOT in mammalian tissues offers hope that agents, which could block either its synthesis or its incorporation into polymers by Actinomyces, would be innocuous to man and might be useful in suppressing the pathogenicity of Actinomyces in dental plaque. Accordingly, an understanding of the biosynthesis of the DOT-containing polymers should expedite the discovery of such useful agents. Success in this endeavor might set a pattern of investigation which, through application to other oral pathogens, might contribute in a major way to the control of dental caries and periodontal disease.